Apparatuses that perform various types of working such as polishing, grinding and lapping have been known in the past as working apparatuses which are constructed to perform working on a worked surface by means of a working tool. One example of such an apparatus is a chemical mechanical polishing apparatus (CMP apparatus) in which the workpiece is a semiconductor wafer, and the working tool comprises a polishing pad that performs surface polishing on this semiconductor wafer. Such CMP apparatuses have conventionally been used in semiconductor device manufacturing processes. CMP apparatuses are used in polishing treatments that polish and flatten films that are formed on the surfaces of wafers in semiconductor wafer manufacturing processes (e.g., the polishing of inter-layer insulating films, the polishing of surface metal films, the polishing of dielectric films, etc.). In such cases, a polishing treatment is required which leaves a uniform and flat film layer of a specified thickness on the surface of the wafer following the polishing treatment. Furthermore, for example, CMP apparatuses include the apparatuses disclosed in Japanese Patent Application Kokai No. H10-303152 and Japanese Patent Application Kokai No. H11-204468.
CMP apparatuses that have generally been used in the past are constructed using a polishing pad having an external diameter that is greater than the external diameter of the semiconductor wafer that is the object of polishing, so that the entire surface that is to be polished on the semiconductor wafer is pressed against the polishing surface of the polishing pad, thus uniformly polishing the entire surface that is to be polished. In this case, uniform polishing can be performed on the entire surface that is to be polished; however, if polishing that is uniform overall is performed in cases where there is an undulating shape with indentations and projections in the film thickness distribution of this surface that is to be polished prior to polishing, this undulation with indentations and projections will still remain in the film thickness distribution of the polished surface following polishing, so that it is difficult to flatten the polished surface, especially in the case of polishing of metal films, STI polishing, etc.